1. Field of the Invention
The present invention relates to an ink-jet printing apparatus and a printing head used in the apparatus, and particularly to a construction which uses a relatively long print head.
In this specification, "printing" includes "textile printing", and "fixing of a dye to a printing medium" includes "fixing of a dye to a printing medium to the extent that substantially no discoloration occurs by washing".
2. Description of the Related Art
A typical example of conventional textile printing methods is a screen textile printing method of printing directly on cloth or the like by using silk screen plates. The screen textile printing method is a method in which a screen plate is formed for each of the colors used in an original image, and cloth is dyed with ink of each color by transferring the ink directly thereto through the meshes of the silk screen.
In this screen textile printing method, many man-hours and days are required for forming the screen plates, and the work of preparing an ink of each of colors required for printing and the work of registering the screen plates are also required. The size of the apparatus used is large and increases in proportion to the number of the colors used, and a large space for installing the apparatus is thus required. A space for storing the screen plates is also required.
On the other hand, an ink-jet recording apparatus has been brought into practical use as a recording apparatus having the function as a printer, a copying machine, a facsimile, etc., and a recording apparatus used as an output device of a composite electronic apparatus and a work station comprising a computer, a word processor, etc. It has been suggested that such an ink-jet recording apparatus be used for textile printing by discharging an ink directly onto a cloth (for example, Japanese Patent Publication Nos. 62-57750 and 63-31594).
In the ink-jet recording apparatus, recording is performed by discharging an ink to a recording material from recording means (recording head). The recording apparatus has the advantages that the recording means can easily be made compact, that a high-definition image can be recorded at a high speed, that the running cost is low, that there is less noise because it is a non-impact system, and that a color image can easily be recorded by using multi-color inks.
Particularly, since the ink-jet recording means (recording head) for discharging ink by utilizing thermal energy comprises electro-thermal converters, electrodes, channel walls, a top plate, etc. which are formed through a semiconductor manufacturing process comprising etching, evaporation, sputtering, etc., recording means having a high-density channel arrangement (arrangement of discharge openings) can readily be produced, and can be made further compact.
A serial type recording apparatus of ink-jet recording apparatuses utilizes a serial scanning system in which horizontal scanning is carried out in a direction perpendicular to the direction of feeding of a recording material (direction of vertical scanning). In this serial type recording apparatus, an image is recorded by recording means loaded on a carriage which is moved in the direction of horizontal scanning along the recording material, the recording material is fed (pitch feeding) for a predetermined length in the direction of vertical scanning after recording is completed for one line, and an image for a next line is then recorded on the stopped recording material. These operations are repeated to record an image over the entire recording material.
On the other hand, in a line type recording apparatus for recording by vertical scanning in the direction of feeding of the recording material, the recording material is set at a predetermined recording position, recording is carried out for one line at a time, the recording material is fed (pitch feeding) for a predetermined length, and recording is then carried out for a next line at a time. These operations are repeated to record an image over the entire recording material. An ink-jet recording apparatus utilizing such line type recording means in which many discharge openings are arranged in the widthwise direction of the recording material enables a further increase in recording speed.
If such an ink-jet recording apparatus is used for textile printing, the screen plates used in screen textile printing need not be used, and thus the numbers of processes and days required to prepare for printing can be significantly decreased. A decrease in size of the apparatus can also be realized.
Even for such an printing apparatus, a increase in printing speed is universally demanded. There have been a proposal of a long head as a construction for increasing the printing speed and many proposals of methods of producing such a long head.
It has been proposed in Japanese Patent Application No. 6-34810 a technology of producing a long head in which substrates (sometimes referred to as "heater boards" hereinafter) each provided with a relatively small number of electro-thermal converters, e.g., 64 or 128 electro-thermal converters, are used as unit substrates, and the heater boards on this unit are precisely arranged and bonded to a base plate. This technology is capable of relatively readily producing a unit substrate having electro-thermal converters arranged with a high precision, and is thus capable of producing a long head at high yield and low cost.
A long head produced by the proposed technology will be described with reference to FIGS. 9 to 14.
FIG. 9 is an exploded perspective view illustrating the construction of a principal portion of such an ink-jet head. The ink-jet head shown in FIG. 9 has 3008 ink discharge openings (printing width 212 mm) with an arrangement density of 360 dpi (discharge opening pitch 70.5 .mu.m).
Referring to FIG. 9, each of unit substrates ("heater boards" hereinafter) 100 is provided with 128 elements 101 for generating energy utilized for discharging ink with a density of 360 dpi. An electro-thermal converter (referred to as "a heater" hereinafter) for applying heat to an ink is used as each of the elements 101. On the heater boards are provided signal pads 102 for enabling supply of signals from the outside with any desired timing, and electric power pads 401 for supplying electric power.
A plurality of the heater boards 100 having the above-described construction are bonded by an adhesive to a portion of a support (base plate) 300 made of a material such as a metal, ceramic or the like along a side of the support in the lengthwise direction thereof. A driving circuit for selectively driving the heaters 101 in accordance with print data is formed on a control circuit substrate 400 which is bonded to the base plate 300 by an adhesive.
A top plate 200 is joined to a portion of the base plate 300 where the heater boards 100 are arranged, so as to be placed on the heater boards 100. The top plate 200 has grooves for forming ink channels and discharge openings corresponding to the respective heaters 101, and a common liquid chamber groove common to the ink channels, which communicates with the ink channels to supply an ink thereto.
FIG. 10 is a cross-sectional view of the heater boards 100 and the base plate 300 taken along the lengthwise direction thereof.
As shown in FIG. 10, the heater boards 100 are bonded to a predetermined portion of the base plate 300 by an adhesive 301 coated to a predetermined thickness. The heater boards 100 are adjacent to each other with the same pitch as the pitch P=70.5 .mu.m of the heaters 101 arranged on the heater boards 100. The spaces between the respective heater boards 100 which are produced by the arrangement thereof are sealed with a sealing agent 302 for preventing leakage of ink.
In FIG. 9, the wiring substrate 400 is bonded to the base plate 300 in the same manner as the heater boards 100, as described above, so that the pads 102 provided on the heater boards 100 and the signal/power supply pads 401 provided on the wiring substrate 400 have a predetermined positional relation. On the wiring substrate 400 is provided a connector 402 for supplying print signals and driving power thereto from the outside.
Description will now be made of the top plate 200 serving as a member with grooves which form channels.
Referring to FIG. 11, the top plate 200 comprises the ink channels 202 respectively provided in correspondence with the heaters 101 provided on the heater boards 100, the discharge openings 203 respectively provided corresponding to the ink channels 202 to discharge ink to a printing medium, the liquid chamber channel 202 communicating with the ink channels 201 to supply ink thereto, and ink supply ports 204 for allowing the ink supplied from an ink tank (not shown) to flow in the liquid chamber channel. The top plate 200 has a length substantially corresponding to a row of the heaters formed by the plurality of heater boards 100.
Description will now be made of the process for joining the top plate serving as a channeled member to the supporting member provided with the plurality of heater boards 100.
A base member in which the plurality of heater boards 100 are bonded to the base plate 300 in accordance with predetermined dimensions is first prepared.
As shown in FIG. 12, the base member is placed at the predetermined position on a base 205 provided on a connecting machine (not shown). The base member is positioned by using pins provided on the base 205. The top plate 200 is then set in a hand 206 of the connecting machine. Predetermined positioning of the top plate 200 is performed by the hand 206. The base plate 300 and the top plate 200 are therefore placed on the base 205 and the hand 206, respectively, so that the positional relation therebetween is set within a range. The positions of the base plate 300 and the top plate 200 are then confirmed by a microscope of the connecting machine. Namely, these positions are confirmed by observing that 1504th heater 101 corresponding to the 1504th discharge opening from the direction shown by axis A in FIG. 12. The accurate position of the 1504th heater in the connecting machine is confirmed by image processing as seen from the direction shown by axis A. Similarly, the position of the discharge opening corresponding to the 1504th heater is confirmed by observing from the direction shown by axis B in FIG. 12. The positions of the base plate 300 and the top plate 200 in direction x shown in the drawing are adjusted so that the position of the discharge opening 203 seen from the direction shown by axis B corresponds to the position of the 1504th heater seen from the direction shown by axis A.
Since the connecting machine has a positioning precision of .+-.2 .mu.m, positioning in the direction x shown in FIG. 12 can be performed with this precision. The hand 206 is then moved downward in direction z with maintaining the same precision to join the top plate 200 to the heater boards 100. The hand 206 is then removed while the top plate 200 is pressed in the direction shown by axis B (direction y) to fix the top plate 200 by springs (not shown).
Although, in this case, the top plate is mechanically pressed by fixing means such as springs or the like, other various means such as an adhesive, combination of an adhesive and springs, etc. may be used. The top plate 200 and the heater boards 100 are thus bonded with the relation shown in FIG. 13.
The top plate 200 can be produced by any of known methods such as a machining method by cutting, a molding method, an injection method, a photolithographic method, etc.
As described above, an ink-jet head can be obtained by mounting the long top plate (channeled member) on the base member comprising the base plate and the plurality of heater boards, each of which has a plurality of heaters and which are arranged on one side of the base plate, so as to cover the heaters of the plurality of heater boards.
The above-described configuration permits the formation of the ink-jet head having simple ink supply paths, and decreases in the size and cost of the head, as compared with an ink-jet head comprising a plurality of small heads each having a top plate provided on a heater board. Since the plurality of heater boards are arranged on only one side of the base plate, electrical wiring can also be simplified. In addition, since the long top plate is mounted on the base member so as to cover the heaters of the respective heater boards, it is possible to prevent the problem that, in an ink-jet head comprising the small heads arranged therein, the channel directions of the respective heads are not uniform. Particularly, when only one top plate is provided, as described above, the directions of all channels can be made uniform by only one registration, and thus a long head producing no shift in printing can be readily obtained.
The aforementioned configuration enables the realization of a long print head which can be practically used.
However, even in the ink-jet head configured as described above, it is impossible to completely solve the problems with respect to shifts of the adhesion positions of the discharged ink droplets caused by small shifts in arrangement of the heater boards, and the nonuniformity of density due to small differences in the amounts of the inks discharged from respective heater boards. The inventors found that differences in density characteristics between respective heater boards are visually remarkable in the portions printed by inks discharged from discharge openings near the boundaries between the respective heater boards.